There are various times that a person needs to carry both a backpack and a gun, and weight is carried much more conveniently using the shoulder and waist belt suspension system of a backpack than when it is carried in a person's arms. For this reason, it is much easier for a person to carry a gun in their backpack than to carry a backpack and a gun separately.
There are prior art gun and scabbard combinations which are designed so that part of the gun extends out of the scabbard and is available for quick and easy retrieval by the person wearing the backpack. The patent applications of the inventor include this feature, and allow a gun to be removed from a scabbard in a backpack without stopping and removing the backpack.
Other situations occur in which protection and concealment of the gun may be more important than rapid withdrawal. In the case of military snipers, if a patrol of soldiers includes a sniper, the enemy may target the sniper with anti-sniper fire, or target the sniper in a fire fight. In such situations, it would be preferable for the sniper in a patrol of snipers to not identify himself as a sniper. In order to do that, it would be desirable to have a pack which had the external appearance of any other pack, but which had a compartment for a concealed weapon.